OPTICAL DESIGN AND PERFORMANCE OF THE PLANETARY FOURIER SPECTROMETER (PFS)

The Planetary Fourier Spectrometer (PFS) is a two-channel Michelson in terferometer operating in the IR from 1.25 to 45 mu m. Two retroreflec tors are mounted on brackets that are at an angle of 90 degrees and fi xed on an axle driven by a torque motor. The angular movement of the r etroreflectors relative to the beam-splitter generates the optical pat h difference. The two primary degrees and the one secondary degree of freedom for misalignment are derived. The pattern of interference frin ges, typical for the different types of misalignment, will be simulate d, and their use for alignment will be demonstrated. This interferomet er design is very robust towards slight misalignment in harsh environm ents, compared to the classical Michelson-type interferometer. This fa vours the design for applications in space. The PFS is intended for th e mission Mars '96. It is optimised for the study of the Martian atmos phere. The spectra will also be used for investigations of the Martian soil.